The Ditsong National Museum of Natural History (formerly the Transvaal Museum) is one of the most important natural history collections in Africa. The building on Paul Kruger Street, a short walk from Church Square, houses collections of African vertebrates, invertebrates, geology, and palaeontology assembled since 1892.
The Mrs Ples skull — the most complete Australopithecus africanus skull ever found, discovered in 1947 at Sterkfontein near Johannesburg — was long the museum's most celebrated exhibit and is still there in some form (the original has moved between institutions). The palaeontological halls contain exceptional material from the Karoo Basin fossil beds. The zoological galleries, while slightly dated in display style, hold extensive type specimens and are used by researchers from across the continent. Worth an hour if you have a serious interest in African natural history or palaeontology.